Method and apparatus for propagating algae culture



r w. JUDA Oct. 7, 1958 METHOD AND APPARATUS FOR PROPAGAT ING ALGAE CULTURE Filed Sept. 20, 1956 TRANSPARENT 's-mnusmnnvr photosynthesis.

'by means of photosynthesis.

United States Patent METHOD AND APPARATUS FOR PROPA- GATING ALGAE CULTURE Walter Juda, Lexington, Mass., assignor to Ionics, In-

corporated, Cambridge, Mass., a corporation of Massachusetts This invention relates generally to process and apparatus for the production of microorganisms capable of More particularly this invention relates to a method and apparatus for propagating an algae culture to effect a rapid, efiicient, and economical multiplication of the same, whereby useful products such as foods, proteins, fats, chlorophyll, vitamins, antibiotics, etc. may be subsequently obtained.

Algae, like other plants containing chlorophyll, are able to convert inorganic compounds into organic matter Although algae vary in size it is the unicellular forms of algae aquatic plants with which this invention is chiefly concerned.

Previous investigations reveal the strong influence of diurnal alternation of light and dark periods in the photosynthesis of microorganisms. The essential light sensitive reaction of photosynthesis stops when the light goes off and resumes when the light comes on. Cell division,

however, may continue during the night at the same rate or even at an increased rate, depending on the temperature at the time and perhaps the preceding history of the culture.

It is furthermore known that the cells of green algae can'utilize in photosynthesis only a small and limited amount of light energy at a time. For example, for Chlorella pyrenoidosa the so-called saturation intensity (i. e. light energies which can be utilized per unit of time in photosynthesis) light is of the order of 400 F. C. (foot candles). On the other hand, in the summer time, incident sun intensity in the middle of the day is at least 8000 F. C. It is apparent then that in optimum conditions of sunlight only 20% of the incident visible energy is utilized for photosynthesis. Thus, the light saturation efiect accounts for the fact that a 20 fold increase in the incident energy results in only a 4 fold increase in the amount utilized by the algae.

Previous attempts for large scale commercial propagation of algae cells were directed to the use of containers with open upper surfaces, flow through transparent plastic tubes, trenches, or open ponds in which the culture is stirred or otherwise prevented from settling. These attempts, however, have certain disadvantages such as lack of protection against dirt and foreign organisms, lack of confinement of nutrient gases (CO etc, and have otherwise proved to be. ineffective, uneconomical and inefficient.

This invention is based upon the principle that algae can utilize light in very short flashes, and particularly an algal cell can absorb etficiently high intensity light in the first stage of photosynthesis and utilize it in comparatively dark areas.

The present invention produces algal cultures in batch or continuous process by spraying droplets or forming films of an aqueous algal suspension containing appropriate nutrients and conditioners, such as nutrient salts, trace minerals, etc. in air which may be appropriately enriched with other nutrient gases such as CO (0.1 to 5%). The fine dispersion or film of algal suspension may be effected in a closed, partially closed or open area with collecting side walls whereby said dispersions, films or droplets are exposed to the full intensity of the rays of natural or artificial sunlight for short periods of time allowing them then to return to the comparative darkness of a culture reservoir. This novel procedure allows for efiicient conversion of intense sunlight in the first stage of photosynthesis. It will also be apparent that the cooling effect which is inherent in the partial evaporation of the films or droplets provides a means for at least partial control of temperature in the apparatus. Thus, in addition to providing eflicient light utilization for photosynthesis, the present invention provides a means for at leastpartial control of temperature through the inherent cooling etfect of evaporation of solution in the finely dispersed or filmlike forms.

It is an object of the present invention to provide process and apparatus which are suitable for large scale production of algae and other microorganisms having photosynthetic capability.

Another object of this invention is to provide an efficient process of the above character which will provide effective and eflicient photosynthesis by algae.

A further object of this invention'is to provide an algal process of the above character having optimum growth and maximum yield.

Another object of this invention is to provide a process and apparatus for continuously producing algae on a large commercial scale.

Another object of this invention is to provide a process which is economical and eflicient with respect to use of light energy and continuous harvesting of algae.

Additional objects and features of the present invention will appear from the following descriptions in conjunction with the accompanying drawings, wherein:

Figure 1 is a schematic side elevational view of apparatus partly in section for carrying out the present invention.

Figure 2 is a similar view of a variation of the apparatus of Figure 1.

Figure 1 of the drawing schematically illustrates apparatus wherein a closed container is employed utilizing continuous recirculation of an algae culture. The apparatus includes means for continuously removing a portion of the culture and continuously introducing feed liquor.

The apparatus consists of a container 1 of any size or shape and is closed at the top by cover 2 as shown in the drawing. Container 1 is preferably round in contour with outwardly flared wall 3 extending from the container 1 to the cover 2. Both cover 2 and wall 3 are made of light transparent material such as glass, transparent plastics, etc. The container 1 has inlet conduit 5 and outlet conduit 6 at opposite sides, each conduit having valves 7 and 8, respectively, to control the rate of feed and product flow. Aheat exchange jacket 9 surrounds container 1 for control of temperature of the liquid algae culture 20. Jacket 9 has entrance and exit connections 19 18 and is connected to suitable means for circulating a cooling or heating fluid therethrough. The conduit 10 extends from the bottom of the container 1 through the jacket 9 and by virtue of pump 11 therein provides for circulation of the liquid medium 20in container 1 into the space above container 1 that is confined between the flared wall 3 and cover 2. A perforated orifice 12, or other spray means, is provided at the outlet of conduit 10 whereby the algae culture is dispersed or sprayed in a fine film into ambient atmosphere of air or carbon dioxide, the latter being provided for by a conduit 13 and outlet 14. A stirrer 16 extending into the liquid medium 20 provides for the proper suspension of said culture in its aqueous medium.

The operation of the apparatus shown in Figure 1 is as follows:

Container 1 is filled at least partially with a nutrient medium 20 inoculated with an appropriate microorganism. The flow of cooling or heating fluid through pipe 19-18 is regulated either manually or preferably autonq t a y qm main th temper tu e f the uid ma i ith n a. an op imum. f .th je qw o h P ul mi o r ni being produ e Su peratures are usually within the range of to 30C. Va 7 i f d. eaded-'51s e ff s d n p p. 11 Withdraws a st ad s ream 9 t eil u j e ium which is maintained in the,fo 1 'm ofasuspension; by .stirrer 11 and forces the sarne through the. sprinkler of sprayer 12 nto t e pe lo ed. ars-9 t ppa a u to o t dir si q o fiaefilm j sai iq i um i contact with the air nd carbondioxide entering into h u er. pace otlths ca tai r thr p p pending upon the force of zthe spray some of the dispe se-s1. q d. medium. wil el h ns the ambient os he baskin e i ete s r 9i ui me i and some will accumnlateon flared wall 3 and return to container 1 in the form of finefilms. The source of light, which may he natural or artificial sunlight, is located above or near the top side of the container, the rays theref rornpenetrating into the. top area of the apparatus. After the growth of the culture has reached a satisfactory level a continuous feed and pr oduct withdrawal is instituted for continuous operation.

Figure 2 schematically.illustrates an open type apparatus wherein outwardly flared side-walled container is provided with feed inlet and product removal conduits 31 and 32 respectively, the liquid medium level 33 being maintained at or below orifice 38 in container 30. Outlet conduit 34 leadingj f rom the bottom of container 30 passes the algae culture from the reservoir 40 through valve 35 into pump 39 which forces the same through control valve 36 into pipe 37 which terminates in an orifice 38 into container'3tl. above the level 33 ofthe culture reservoir 40.

It is apparent that the operation of the apparatus of Figure 2 is verysirnilar to the apparatus of Figure '1. The temperature of the algae culture is liege retained below 30 C. by virtureof the inherent partial evaporation of thethin film and fine dispersion of the algae culture in theopen atmosphere of the upper portion of container 3i Furthermore, no provision for carbon dioxide in the atmosphere need be made since thefarnbient atmosphere is often sufficient for the purpose. It is clear that there is a continuous recycle of the algae culture from the reservoir 4 0 .through'the orifice 38 at the top of spray conduit 37; and with sunlight penetrating into the upper atmosphere of containe 30. An intermittent photosynthesis of the algae culture will be effected in a continuous efficient and economicalmanner.

The following examples are given byway of illustration, but not as necessarily limiting the scope of the invention: v l

Example I The apparatus of Figure 1 was used, :with a suspension of Chlorella pyrenoidosa at. a concentration of 0.36 gm. dryweight per liter of solution. The aqueous suspension in the container contained the following nutrient chemicals in solution:

adjusted with HCl to pH 6.0.

The feed solution contained'the above nutrients without any algae,-but with-entrainedair with 5% by volume of added C0 The jacket was. used to maintain the temperature at 22 C.,. and thepump recirculated and atomized the suspension into. a fine spray which settled back into the container after exposure tolight in the upper portion of the. container. Gas: was withdrawn,

'lation and dispersion enriched in oxygen and depleted in CO A continuous overflow of product was maintained, at a rateof 5 mlJrninutc, adjusted to provide a constant Chlorella concentration of 0.3 gm. dry weight per liter.

Example The apparatus of- Figure 2 was fed with the nutrient solution of Example 1 after initially seeding the open trough with Chlorella at a concentration of 0.25 gm. dry weight/liter. A product of this composition was withdrawn at a rate of 1 liter per hour.

Having thus disclosed my invention and described in detail preferred embodiments thereof so that any person skilled in the art may practice'it, I claim and desire to secure by Letters Patent:

1. In the photosynthesis of aculture of microorganisms in a nutrient medium including nutrient salts for microorganisms, air and carbon dioxide, the step of continuously forming a fine dispersion of atleast a portion of said culture'in the presence of light until a desired predetermined density of said microorganismsis obtained.

2. 1n the photosynthesis. of algae in liquid -mediacontaining nutrients therefor, the steps of withdrawing at least a portion of said medium from a' reservoirthereof, dispersing the same in the form of fine particles into an atmosphere containing oxygen and carbon dioxide the presence of light, returning the light treated particles in the form of fine films of liquid medium to the reservoir thereof, and continuously repeatingthe operation until a desired predetermined density of algae cells is obtained.

3. The process of claim 2 which includes the step of continuously feedingand bleeding liquid medium and product respectively to provide for continuous large scale operation.

4. Theprocess of claim 2 wherein the forming of the fine dispersion of the culture'is obtained byintermittant spraying of the same.

5. Apparatus for the continuous cultureand harvesting of Chlorella and like photosynthetic microorganisms, comprising a container having outwardly flared walls at the top section of said container and adapted to admit light to the interior thereof, means for continuously 'introducing andrernoving controlled amounts of aqueous nutrient containing liquid 'inthe bottom section of said container, means for continuously withdrawing portions of said nutrient-containing liquid from thehot tom of said container, and means for continuously spraying said withdrawn liquid into the atmosphere at the topflared walled section with sufiicient force to cause said spray to form films of the dispersed fine-particles of liquid in contact with said outwardly 'flared walls of the upper section of said container whereby a continuous recircuof said nutrient liquid exposed to light is effected.

6. The apparatus of claim 5 wherein the container is closed by a light transparent cover at the top thereof, and means in the upper section of said container for introducing and withdrawing nutrient gases in said container.

7; The apparatus of claim 5 wherein the topof said outwardly flared walled ocntainer is open to the ambient atmosphere. i l I References Cited in the file. of this patent UNITED STATES PATENTS.

Matzka ..Dec. 27, 1927 Myers lan iil, 1956 OTHER REFERENCES ,Kingzetts Chemical Encyclop aedia, Edition, Published 1952 byBailliere Tiridall .and ,Qox"(London, England). Pages 322 through 325,,

' Algal Culture (Burlew), Published 1953 by Carnegie Institution of Washington (D. (3.), .a sluhlication 600. Pages 16, 135, 136, 137, 138, 275. 

1. IN THE PHOTOSYNTHESIS OF A CULTURE OF MICROORGANISMS IN A NUTRIENT MEDIUM INCLUDING NUTRIENT SALTS FOR MICROOGANISMS, AIR AND CARBON DIOXIDE, THE STEP OF CONTINOUSLY FORMING A FINE DISPERSION OF AT LEAST A PORTION OF SAID CULTURE IN THE PRESENCE OF LIGHT UNTIL A DESIRED PREDETERMINED DENSITY OF SAID MICROOGANISM IS OBTAINED. 